scholarly journals Two paradigms of population regulation

1995 ◽  
Vol 22 (1) ◽  
pp. 1 ◽  
Author(s):  
C. J. Krebs
Keyword(s):  
Population Density ◽  
Density Dependence ◽  
Population Regulation ◽  
Food Shortage ◽  
Holy Grail ◽  
Density Dependent ◽  
Movement Rates ◽  
Birth Death

No population increases without limit and ecologists have utilised two paradigms to find out why. The density-dependent paradigm assumes that birth, death and movement rates will be related to population density. In many cases they are not, and the search for density dependence has become a holy grail. A better approach is through the mechanistic paradigm which searches for relationships between birth, death and movement rates, and the mechanisms controlling populations, such as disease, predation, food shortage and territoriality. Seven suggestions are made for analysing the role of disease in population regulation in mammals. Useful progress will flow more quickly from the mechanistic paradigm without the need to search for density dependence.

Density-Dependent Population Growth

2020 ◽  
pp. 29-46
Author(s):  
Michael J. Fogarty ◽  
Jeremy S. Collie
Keyword(s):  
Population Density ◽  
Population Growth ◽  
Density Dependence ◽  
Multiple Equilibria ◽  
Dynamical Behavior ◽  
Logistic Growth ◽  
Density Dependent ◽  
Per Capita ◽  
Discrete Time Models ◽  
Complex Dynamical Behavior

The observation that no population can grow indefinitely and that most populations persist on ecological timescales implies that mechanisms of population regulation exist. Feedback mechanisms include competition for limited resources, cannibalism, and predation rates that vary with density. Density dependence occurs when per capita birth or death rates depend on population density. Density dependence is compensatory when the population growth rate decreases with population density and depensatory when it increases. The logistic model incorporates density dependence as a simple linear function. A population exhibiting logistic growth will reach a stable population size. Non-linear density-dependent terms can give rise to multiple equilibria. With discrete time models or time delays in density-dependent regulation, the approach to equilibrium may not be smooth—complex dynamical behavior is possible. Density-dependent feedback processes can compensate, up to a point, for natural and anthropogenic disturbances; beyond this point a population will collapse.

scholarly journals Increased natural mortality at low abundance can generate an Allee effect in a marine fish

2014 ◽  
Vol 1 (2) ◽  
pp. 140075 ◽  
Author(s):  
Anna Kuparinen ◽  
Jeffrey A. Hutchings
Keyword(s):  
Population Dynamics ◽  
Population Growth ◽  
Density Dependence ◽  
Gadus Morhua ◽  
Allee Effect ◽  
Population Regulation ◽  
Atlantic Cod ◽  
Adult Mortality ◽  
Natural Mortality ◽  
Density Dependent

Negative density-dependent regulation of population dynamics promotes population growth at low abundance and is therefore vital for recovery following depletion. Inversely, any process that reduces the compensatory density-dependence of population growth can negatively affect recovery. Here, we show that increased adult mortality at low abundance can reverse compensatory population dynamics into its opposite—a demographic Allee effect. Northwest Atlantic cod ( Gadus morhua ) stocks collapsed dramatically in the early 1990s and have since shown little sign of recovery. Many experienced dramatic increases in natural mortality, ostensibly attributable in some populations to increased predation by seals. Our findings show that increased natural mortality of a magnitude observed for overfished cod stocks has been more than sufficient to fundamentally alter the dynamics of density-dependent population regulation. The demographic Allee effect generated by these changes can slow down or even impede the recovery of depleted populations even in the absence of fishing.

Role of Nest Raiding and Egg Predation in Regulating Population Density of Threespine Sticklebacks (Gasterosteus aculeatus) in a Coastal British Columbia Lake

1989 ◽  
Vol 46 (3) ◽  
pp. 372-383 ◽  
Author(s):  
Kim D. Hyatt ◽  
Neil H. Ringler
Keyword(s):  
British Columbia ◽  
Population Density ◽  
Gasterosteus Aculeatus ◽  
Population Regulation ◽  
Egg Predation ◽  
Coastal Lake ◽  
Egg Consumption ◽  
Threespine Sticklebacks ◽  
Coastal British Columbia

The consequences of nest raiding and egg predation for population regulation of sticklebacks (Gasterosteus aculeatus) were studied in a British Columbia coastal lake. Stickleback eggs were present in the stomachs of 23 and 11% of all sticklebacks sampled from the field in 1982 and 1985 respectively. On average, males consumed more eggs than did females. Seasonal egg consumption increased with increases in stickleback density in breeding colonies. In experimental enclosure studies, nest densities varied between 0 and 3∙m−2 as stickleback numbers were manipulated from 1.5 to 12∙m−2. Peak nest densities occurred at 5.8 fish∙m−2. Stickleback density explained 70–86% of the variation in nest numbers in an application of a Ricker stock–recruit model and weekly rates of nest survival exhibited strong density dependence. Our evidence indicates that both nest raiding and egg cannibalism are important in limiting the production of stickleback fry as population density increases in scattered, lakeshore, breeding colonies of Kennedy Lake.

scholarly journals Population Density or Populations Size. Which Factor Determines Urban Traffic Congestion?

2021 ◽  
Vol 13 (8) ◽  
pp. 4280
Author(s):  
Yu Sang Chang ◽  
Sung Jun Jo ◽  
Yoo-Taek Lee ◽  
Yoonji Lee
Keyword(s):  
Population Density ◽  
Population Size ◽  
Traffic Congestion ◽  
Critical Role ◽  
Small Population ◽  
High Density ◽  
Urban Traffic ◽  
Contradictory Result ◽  
Low Density

A large number of articles have documented that as population density of cities increases, car use declines and public transit use rises. These articles had a significant impact of promoting high-density compact urban development to mitigate traffic congestion. Another approach followed by other researchers used the urban scaling model to indicate that traffic congestion increases as population size of cities increases, thus generating a possible contradictory result. Therefore, this study examines the role of both density and population size on traffic congestion in 164 global cities by the use of Stochastic Impacts by Regression on Population, Affluence and Technology model. We divide 164 cities into the two subgroups of 66 low density cities and 98 high density cities for analysis. The findings from the subgroups analysis indicated a clear-cut difference on the critical role of density in low-density cities and the exclusive role of population size in high-density cities. Furthermore, using threshold regression model, 164 cities are divided into the two regions of large and small population cities to determine population scale advantage of traffic congestion. Our findings highlight the importance of including analysis of subgroups based on density and/or population size in future studies of traffic congestion.

The role of density-dependence regulation in the misleading effect of the Aznalcollar mining spill on the booted eagle fecundity

2017 ◽  
Vol 583 ◽  
pp. 440-446 ◽  
Author(s):  
Esperanza Gil-Jiménez ◽  
Javier Manzano ◽  
Eva Casado ◽  
Miguel Ferrer
Keyword(s):  
Density Dependence

scholarly journals Effect of school reopening on SARS-CoV-2 incidence in a low-prevalence region: Prospective SARS-CoV-2 testing in healthcare workers with primary school-attending children versus without children living at home

2021 ◽  
pp. 175717742110124
Author(s):  
Melvin Frie ◽  
Lisa M Havinga ◽  
Janneke Wiersema-Buist ◽  
Charlotte G Veldman ◽  
Marjan JT de Vries ◽  
...  
Keyword(s):  
Cohort Study ◽  
Population Density ◽  
Severe Acute Respiratory Syndrome ◽  
Primary School ◽  
Primary Schools ◽  
Healthcare Workers ◽  
Regional Strategies ◽  
Low Prevalence ◽  
At Home

Coronavirus disease 2019 (COVID-19) often presents asymptomatically or milder in children compared to adults. The role of young children in the transmission of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) remains largely unknown. In the Netherlands, the first action of loosening the partial lockdown that had been implemented to reduce SARS-CoV-2 transmission was the reopening of primary schools on 1 May 2020. We subsequently conducted a prospective cohort study among healthcare workers (HCWs) with primary school-attending children versus HCWs without children living at home. We tested each HCW three times for SARS-CoV-2 from May 20 to June 15 2020 at 1-week intervals. In total, 832 nasopharyngeal swabs were taken from 283 HCWs with primary school-attending children living at home and 864 nasopharyngeal swabs from 285 HCWs without children living at home. All nasopharyngeal swabs tested negative for SARS-CoV-2. In our region with a low population density and low SARS-CoV-2 prevalence, reopening of primary schools did not lead to an increase in infections. The results of this study may serve as an example for the implementation of regional strategies to reduce SARS-CoV-2 transmission in countries with large variations in both population density and SARS-CoV-2 prevalence.

scholarly journals Size-mediated, density-dependent cannibalism in the signal crayfish Pacifastacus leniusculus (Dana, 1852) (Decapoda, Astacidea), an invasive crayfish in Britain

Crustaceana ◽  
2017 ◽  
Vol 90 (4) ◽  
pp. 417-435 ◽  
Author(s):  
R. J. Houghton ◽  
C. Wood ◽  
X. Lambin
Keyword(s):  
Relative Size ◽  
Pacifastacus Leniusculus ◽  
Gut Contents ◽  
Size Distributions ◽  
Signal Crayfish ◽  
Density Dependent ◽  
Invasive Crayfish ◽  
The Relationship ◽  
Best Fit

The role of cannibalism in crayfish populations is not well understood, despite being a potentially key density-dependent process underpinning population dynamics. We studied the incidence of cannibalism in an introduced signal crayfish Pacifastacus leniusculus population in a Scottish lowland river in September 2014. Animals were sampled using six different sampling techniques simultaneously, revealing variable densities and size distributions across the site. Cannibalism prevalence was estimated by analysing the gut contents of crayfish >20 mm CL for the presence of crayfish fragments, which was found to be 20% of dissected individuals. When seeking evidence of relationships between the sizes of cannibals and ‘prey’, the density of conspecifics <56% the size of a dissected individual yielded the best fit. The relationship between cannibalism probability and crayfish size and density was equally well described by three different metrics of crayfish density. Cannibalism increased with crayfish size and density but did not vary according to sex. These results suggest that large P. leniusculus frequently cannibalize smaller (prey) conspecifics, and that the probability of cannibalism is dependent upon the relative size of cannibal-to-prey and the density of the smaller crayfish. We suggest that removing large individuals, as targeted by many traditional removal techniques, may lead to reduced cannibalism and therefore a compensatory increase in juvenile survival.

Sign in / Sign up

Export Citation Format

Share Document